In our daily lives, a hot laminating apparatus (also referred as a laminator) is widely used for protecting a sheet article such as a document or a photo. After a sheet article is sandwiched between two thermoplastic films, the sheet article and the two thermoplastic films are fed into the laminator, and the sheet article and the two thermoplastic films are hot pressed (or laminated) by the laminator. Consequently, two protective films are formed on both surfaces of the sheet article in order to protect the sheet article.
FIG. 1 is a schematic view illustrating a conventional hot laminating apparatus. As shown in FIG. 1, the hot laminating apparatus 1 comprises a heating mechanism 10, two pressing rollers 11 and a transmission channel 12. The heating mechanism 10 is used for transforming electricity into heat energy. The heat energy generated by the heating mechanism 10 is transferred to the pressing rollers 11 through air in order to heat up the pressing rollers 11. When a sheet article sandwiched between an upper thermoplastic film and a lower thermoplastic film (not shown) is fed into the hot laminating apparatus 1 through an entrance of the transmission channel 12, the pressing rollers 11 which have been heated up by the heat energy may laminate these two thermoplastic films. Since the two thermoplastic films are heated and softened, the sheet article can be fixed between the two thermoplastic films.
For enhancing the laminating efficacy, the hot laminating apparatus 1 should be adjusted to a proper laminating temperature according to the thickness of the sheet article to be laminated. If the sheet article to be laminated is too thick, it is required to take a long time for waiting the pressing rollers 11 to heat up a corresponding preheating temperature. After the pressing rollers 11 are heated to the preheating temperature, the two thermoplastic films and the sheet article between these two thermoplastic films can be fed into the transmission channel 12 to be laminated by the pressing rollers 11. In other words, the operations of the conventional hot laminating apparatus 1 are not user-friendly. Therefore, it is an important issue to research how to shorten the preheating time of the conventional hot laminating apparatus 1.
Moreover, after the two thermoplastic films and the sheet article between these two thermoplastic films are introduced into the transmission channel 12, at least one of the two pressing rollers 11 is shifted. Consequently, the two pressing rollers 11 are separated from each other by a gap. The gap is substantially equal to the overall thickness of the two thermoplastic films and the sheet article. In such way, the two thermoplastic films and the sheet article can be transmitted through the region between the two pressing rollers 11, and the two thermoplastic films and the sheet article can be clamped by the two pressing rollers 11 collaboratively. For preventing the shifted pressing roller 11 from compressing the heating mechanism 10, it is necessary to have a sufficient spacing distance D between the installation position of the heating mechanism 10 and the installation position of each pressing roller 11. That is, the spacing distance D should be larger than a maximum distance that the pressing roller 11 can be shifted.
However, the applicants found that the heat energy generated by the heating mechanism 10 fails to be effectively transferred to the pressing rollers 11 because the spacing distance D between the heating mechanism 10 and the pressing roller 11 is usually too large. This is also the reason why the heating time of the conventional hot laminating apparatus 1 fails to be effectively shortened. Therefore, there is need of providing a hot laminating apparatus with a faster preheating speed and preventing the shifted pressing roller 11 from compressing the heating mechanism 10.